JPH01170790A - Vertical shaft turbo pump capable of varying critical velocity - Google Patents

Abstract

PURPOSE:To vary the critioal velocity of a shaft hy controlling the quantjty bi a liquid injected and diecharged into md from a hollow portion formed in the vioinity oi the central portion oi a mtary shaft of a pump. CONSTITUTION:The vioinity of the central portion in the long/itudinal dlrection oi a rotary sbaft 1' of a vertioal s1]aft turho pump is oonstructed like a hollow pfpe to form a spBoe 4. A Suction and ezhaust hole 5 for connecting the space d and the suction side ol the,mp and a suctSon and exhaust hole 6 for connecting the spaoe 4 and the upper ehd of the rotary shaft are provided to be conneoted to a gas pressure control device. Operating fluid in the pump is sucked and discharged through the suotjon and exhaust hole 5 in and from the space 4 by controlling the gas pressL]re of tbe gas pressure control device. When the pump js.rotated at low speed, a llquid ia ooa]tletely disotrged from the rotary shaft hollow portion 4 to iroreaee the oritical Velocity. when the pump is rotated at high speed, a liquid is stayed in the hollow portion 4 to iDorease the weight of the shBft and deorease the critioal velocjty. when the crjtlcal velocity is thns varied, thc shafh is kept from resonencc in the critlcal velocity, so iil]at the designed rotational frequency can be set high. Aocordingly, the impeller and shaft can be reduced in diameter, and the pump can be reduced in size.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a vertical shaft turbo pump, and particularly to a shaft turbo pump that has been improved to be suitable for use as a sodium pump for fast breeder reactors. be.

[Conventional technology]

The latest technology related to sodium pumps is
No. 7-8318r Liquid Metal Pump" is known.

FIG. 3 shows a longitudinal sectional view of a conventional sodium pump for a fast breeder reactor.

Due to the system design, sodium pumps for fast breeder reactors are shaft pumps with relatively long shaft lengths. Furthermore, since the pump has a free liquid surface structure, the distance between the bearings is long. Further, since the pump is controlled in rotation speed within a range of approximately 10 to 100% of the design rotation speed, the design rotation speed of the pump is set to a rotation speed sufficiently lower than the critical speed of the shaft system.

In the conventional technology, the critical speed is designed to be as high as possible compared to the rotational speed within the operating condition range, and a safety margin (rotational speed difference) is provided between the rain noises.

The reason why the rotary shaft 1 of the conventional example shown in FIG. 3 has a hollow tube shape near its center is to be as light as possible and increase rigidity to reduce the critical speed from a high level.

[Problems to be solved by the invention] Because the sodium pump for fast breeder reactors has a system structure with a long shaft length and bearing span, and the rotation speed is controlled, the pump rotation speed is designed to be within a range sufficiently lower than the critical speed. There is a need to.

From the viewpoint of the water pumping performance of the pump, the higher the design rotation speed of the pump, the smaller the impeller diameter can be.

However, if an attempt is made to increase the design rotational speed, the shaft diameter of the pump will become larger, and there is a problem in that even if the rotational speed is increased unnecessarily, it will not lead to a reduction in the weight of the pump or a reduction in the diameter of the pump.

SUMMARY OF THE INVENTION An object of the present invention is to provide a compact pump that can have a high design rotational speed and reduce the diameter of the impeller and shaft while ensuring the safety of the pump.

[Means for solving problems]

The critical speed in a spindle turbo pump is, in short, the rotational speed at which the rotating shaft may cause resonance.

Therefore, in the prior art, the practical rotational speed was set on the lower side than this critical speed.

However, in order to avoid resonance, it is also possible to set the practical rotational speed higher than the critical speed.

Conventional technology has been unable to break away from the fixed idea that the critical speed must be increased in order to increase the practical rotational speed, and has not been able to meet the demand for smaller and faster sodium pumps.

The present invention makes the critical speed of the pump variable.

When the pump is rotated at high speed, the critical speed is adjusted to below the practical rotational speed to ensure safe operation.

As a specific means for changing the critical speed, a means for injecting (or inhaling) a liquid into a hollow part provided in the center of the one-rotation shaft or discharging the liquid is provided.

[Effect]

When a spindle turbo pump configured as described above is operated at low speed, the critical speed is increased by draining all the liquid from the hollow part of the rotating shaft, and the critical speed is sufficiently higher than the pump rotation speed. This ensures safe operation with less vibration. In addition, when the pump is operated at high speed, the critical speed is lowered by storing liquid in the hollow part and increasing the weight of the shaft, and the critical speed is sufficiently lower than the pump rotation speed to reduce vibration. Safe driving can be ensured.

〔Example〕

FIG. 1 is a sectional view showing an example of applying the present invention to a sodium pump for a fast breeder reactor. It has a liquid level of 7.

The rotating shaft 1 is supported by a bearing 2 at the upper part and a bearing 3 at the lower part.

Reference numeral 1' denotes a rotating shaft, and a space 4 is formed by forming a hollow tube near the central portion in the longitudinal direction.

A supply/discharge hole 5 connecting the space 4 and the suction side of the pump and a supply/discharge hole 6 connecting the space 4 to the upper end of the rotating shaft are provided.

The supply/discharge hole 6 is connected to a gas pressure control device for argon gas which does not react with sodium.

The working fluid of the pump is supplied and discharged into the space 4 through the supply and discharge hole 5 by controlling the gas pressure of the gas pressure control device.

FIG. 2 shows a different embodiment from the one described above, with the zero rotation axis 1' having
A space 4, a supply/discharge hole 5' connecting the space 4 to the upper end of the rotating shaft 1, a supply/discharge pipe 8 extending from the supply/discharge hole 5 to the lower part of the space 4, and a supply/discharge hole 5' bored near the upper end of the space 4. A discharge port 6' is provided.

The above-mentioned supply/discharge hole 5' is connected to a liquid supply/discharge control device at the upper end of the rotating shaft 1'. The liquid supply control device supplies and discharges a liquid having a high specific gravity such as mercury to the space 4 through the supply and discharge hole 5' and the supply and discharge pipe 8.

During the above-mentioned supply and discharge operation, the supply and discharge port 6' performs a breathing action,
The pressure in space 4 is automatically adjusted.

〔Effect of the invention〕

According to the present invention, since the critical speed of the pump can be variably controlled, it has the excellent practical effect of making it possible to increase the pump rotation speed without unnecessarily increasing the shaft diameter. This greatly contributes to the miniaturization and higher performance of pumps.

[Brief explanation of the drawing]

1 and 2 are longitudinal cross-sectional views of an embodiment of a vertical shaft turbo pump according to the present invention, respectively. FIG. 3 is a vertical sectional view showing a conventional vertical shaft turbo pump. 1.1'...Rotating shaft, 2,3...Bearing, 4...Inner space of the hollow part formed near the center of the rotating shaft, 5゜5
'... Supply/discharge hole, 6... Supply/discharge hole, 6'... Supply/discharge port,
7... Free liquid level, 8... Supply/discharge pipe.

Claims (1)

[Claims] 1. A vertical shaft turbo type having a rotating shaft, a plurality of bearings supporting the rotating shaft, an impeller attached to the rotating shaft, and a casing provided outside the impeller. In the pump, (a) at least the vicinity of the central portion of the rotating shaft is hollow, (b) a supply/discharge port is provided for injecting and discharging liquid into the hollow portion, and (c) the inside of the hollow portion is hollow. A vertical shaft turbo pump with variable critical speed, characterized by a structure that allows adjustment of liquid volume. 2. (d) The rotating shaft has a supply/discharge hole that communicates between the hollow portion formed near the center and both ends of the rotating shaft, and (e) The rotating shaft communicates with the upper end of the rotating shaft. The vertical shaft turbo type with variable critical speed according to claim 1, characterized in that the supply/discharge hole is provided with a pipe line for communicating gas pressure, and a means for adjusting the gas pressure. pump. 3. (f) The rotating shaft has a supply/discharge port formed in the pipe wall near the upper end of the hollow tubular part formed near the center thereof, and (g) the inner space of the hollow tubular part and the upper end of the rotating shaft. and (h) connecting a conduit for pumping, injecting and suctioning and discharging liquid to the supply and discharge hole communicating with the upper end of the rotating shaft, (i) inside the hollow tubular part. A patent claim characterized in that a supply/discharge pipe is provided, the upper end of the supply/discharge pipe is connected to the supply/discharge hole of item (g), and the lower end of the supply/discharge pipe is located near the lower end of the hollow tubular part. Vertical shaft turbo pump with variable critical speed as specified in Range 1.